Achieving learning standards is at the forefront of current educational philosophy, and is the goal of sound educational practice. That "all children can learn" and there will be "no child left behind" presume that teaching and assessment practices must benefit all children. Agreement in principle is nearly universal. Practical implementation, however, is another matter. One philosophy of learning and instruction that has a long history of targeting instruction and achievement for all students is mastery learning. This article examines (a) fundamental tenets that mastery learning is built upon, (b) the clear connection between learning standards and mastery learning, and (c) how mastery is often erroneously implemented. It then outlines the defining features of mastery and how to implement them. These defining features include developing clear objectives, setting a mastery standard, using criterion-referenced assessments, and grading incentives for students to learn beyond initial mastery. (Contains 1 figure.)